Strategies and optimized workflow for AF ablation
At the 28th Annual Scientific Congress of the Hong Kong College of Cardiology, Dr Songwen Chen of the School of Medicine at Jiao Tong University, Shanghai, China, discussed image integration, types of pulmonary vein (PV) isolation and use of novel markers in the context of the available strategies and workflow optimization for atrial fibrillation (AF) ablation.
Up until recently, the conventional index for ablation accuracy has been the distance comparison between mapping points. However, a study in 48 patients treated for AF at Shanghai Jiao Tong University has found that both the angle and the distance can be significantly reduced by navigation with image integration, but the angle exhibited better sensitivity than the conventional index of distance. “Our results justify using the angle in combination with the conventional distance index to provide a more sensitive index of ablation accuracy,” said Chen. [The Heart Surgery Forum 2018;21:E438-E442]
“PV isolation is considered the cornerstone of catheter ablation for the treatment of AF,” stated Chen. Catheter ablation is a potentially curative treatment option for patients with AF, particularly for those with paroxysmal AF. In the past two decades, the procedure has evolved from the ablation of focal AF triggers inside the PVs to wide-area circumferential PV antrum isolation (PVAI). [Circ Arrhyth Electrophysiol 2012;5:667-675]
A study, which enrolled 101 consecutive patients with paroxysmal AF, sought to determine the relationship between the size of the left atrial isolated surface area (ISA) after PVAI and rhythm outcome. At 12-month follow-up, a larger ISA was associated with a significantly lower AF and macroreentrant tachycardia recurrence rate. “ISA of 55 percent or greater may serve as a predictor for long-term success after PVAI,” concluded the researchers. [Circ Arrhyth Electrophysiol 2012;5:667-675]
“In addition to ISA, another variable is the approach used for PV isolation: ostial or wide antral,” said Dr Chen. “A review of 12 clinical trials indicates that the wide antral approach is more effective than ostial PVI in achieving freedom from total atrial tachyarrhythmia recurrence at long-term follow-up.” [Circ Arrhythm Electrophysiol 2014;7:39-45]
“A common ablation challenge is force control,” continued Chen. “It is a balancing act between efficacy and safety. A light contact is usually associated with a lengthy procedure, may be insufficient, and may necessitate a repeat procedure in up to 30 percent of cases; the effectiveness of this approach varies widely between centres. On the other hand, excessive contact runs the risk of tamponade, oesophageal injury and steam pops.”
The ablation index (AI) and lesion size index (LSI) are novel markers for predicting ablation lesion quality. However, collateral damage is still a concern. A study in an ex vivo model based on swine myocardium compared lesion characteristics and tissue temperature profiles produced under ablation settings between 20 W and 40 W. It established that although the targeted AI and LSI were the same for both 20 W and 40 W, the tissue temperature profiles differed greatly depending on the radiofrequency power setting. “A high-power setting based on the AI and LSI may reduce the collateral thermal damage,” concluded the researchers. [J Cardiovasc Electrophysiol 2020;31:196-204]